CN102854610B - Pick-up lens - Google Patents
- ️Wed Dec 21 2016
CN102854610B - Pick-up lens - Google Patents
Pick-up lens Download PDFInfo
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Publication number
- CN102854610B CN102854610B CN201210221974.3A CN201210221974A CN102854610B CN 102854610 B CN102854610 B CN 102854610B CN 201210221974 A CN201210221974 A CN 201210221974A CN 102854610 B CN102854610 B CN 102854610B Authority
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- lens
- diffractive optical
- chromatic aberration
- imaging
- aberration Prior art date
- 2011-06-30 Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/004—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having four lenses
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Lenses (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
The present invention provide a kind of be suitable to the small-sized and imaging apparatus of high density pixel and suitably correct aberration, high image quality, low cost, small-sized pick-up lens.It is made up of the 1st lens, the 2nd lens, the 3rd lens, the 4th lens successively from object side, lensed two sides is formed by aspheric surface, and in the face of object side of the 1st lens to forming the diffraction optics face playing chromatic aberration correction function on any one face in the face of the object side of the 3rd lens, it is molded of plastic material all lens.
Description
Technical Field
The present invention relates to an imaging lens for forming an image of an object on an imaging Device such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and more particularly to a compact imaging lens mounted on a mobile information terminal (PDA) such as a mobile phone.
Background
In recent years, most mobile phones have a camera function mounted thereon. Recently, mobile phones equipped with a high-resolution camera function comparable to a digital still camera (digital still camera) have also appeared. In addition, an imaging device that realizes such a camera function is increasingly downsized in response to the demand for downsizing and thinning of a mobile phone. The imaging lens incorporated in the imaging device is also inevitably strongly required to be miniaturized. Further, there is a strong demand for an imaging lens having high optical performance that can be sufficiently applied to an imaging element with higher pixels and higher resolution.
With the miniaturization and high pixel density of imaging devices, the pixel size has become increasingly finer and denser. Recently, image pickup elements having a pixel pitch of less than 1.4 μm have been proposed. The performance required of an imaging lens corresponding to such an imaging element is not sufficient, but the aberration is small. Further, there is a strong demand for a bright optical system having sufficient resolution, i.e., a large aperture ratio of a lens. Conventionally, an imaging lens having a 3-lens structure has been proposed, but an imaging lens having a 4-lens structure and a 5-lens structure has also been proposed in order to be applied to the imaging device.
For example, an imaging lens disclosed in patent document 1 is composed of, in order from an object side, a positive 1 st lens whose object side surface is convex, a negative 2 nd lens whose concave surface faces an image plane side, a positive 3 rd lens whose convex surface faces the image plane side and is meniscus, and a positive or negative 4 th lens whose both surfaces are aspherical and whose image plane side surface is concave near an optical axis. In this configuration, by setting the abbe numbers of the 1 st lens and the 2 nd lens within a preferable range, a correction effect of chromatic aberration on axis and chromatic aberration of magnification can be obtained; by setting the ratio of the focal lengths of the 2 nd lens and the 1 st lens and the ratio of the focal lengths of the 3 rd lens and the 4 th lens within the preferable ranges, it is possible to secure the telecentric (telecentric) characteristic and to perform correction of chromatic aberration on the axis and chromatic aberration of magnification while securing miniaturization of the entire lens system.
Further, the imaging lenses disclosed in patent documents 2 and 3 have a structure of 5 lenses, thereby solving the problem of the structure of 4 lenses, and practical lenses have been proposed.
Patent document
Patent document 1: japanese patent laid-open publication No. 2007-219079
Patent document 2: japanese laid-open patent publication No. 2007-264180
Patent document 3: japanese laid-open patent application No. 2010-197665
Disclosure of Invention
According to patent document 1, a relatively good aberration can be obtained. However, in order to obtain sufficient resolution while corresponding to the above-described image pickup element with a reduced size and a higher density, a large aperture ratio of about F/2.4 is required. In patent document 1, Total Track Length (TTL) is long, and therefore miniaturization is difficult. Further, it is difficult to achieve good aberration correction while securing a large aperture ratio. Patent documents 2 and 3 have proposed practical lenses to solve the problem of 4-lens imaging lenses, but the number of imaging lenses is large, which is disadvantageous for cost reduction. In addition, since a lens sensitive to manufacturing tolerance is often used, the manufacturing cost is also disadvantageous. Further, the glass material is used in many ways, which is not favorable for cost reduction. Further, in patent documents 2 and 3, when a plastic lens is selected for cost reduction, there are few material options, and it is difficult to achieve both chromatic aberration correction and other aberration correction.
In view of the above-described problems of the prior art, an object of the present invention is to provide an imaging lens that is compact, can effectively correct chromatic aberration, can correct other aberrations well, has a large aperture ratio, and has high performance, in accordance with the recent thinning of a mobile phone.
In order to solve the above problems, the present invention is configured by arranging a 1 st lens, a 2 nd lens, a 3 rd lens, and a 4 th lens in this order from an object side, forming both surfaces of all the lenses by aspherical surfaces, and forming a diffractive (diffraction) optical surface that exhibits a chromatic aberration correction function on any one of an object side surface of the 1 st lens to an object side surface of the 3 rd lens, and configuring all the lenses by a plastic material.
With the above configuration, each aberration can be corrected well, and good correction of chromatic aberration can be achieved by forming the diffractive optical surface on the most appropriate surface.
The diffractive optical surface is composed of undulations (relief) that produce optical path differences defined as a function of the optical path differences. The abbe number of the e-line of the diffractive optical surface is about-3.3 with respect to the abbe number of 25 to 80 in the e-line of a general glass material, and has a property of showing dispersion (dispersion) of about one big bit in minus sign. In order to correct chromatic aberration, it is known to combine at least two materials having different chromatic dispersion, but chromatic aberration correction can be more effectively achieved by further forming a diffractive optical surface on an appropriate surface.
In a general lens system not using a diffractive optical surface, a lens of a high chromatic dispersion material for chromatic aberration correction is generally arranged at a position close to an aperture stop. Similarly, by disposing the diffractive optical surface also at a position close to the aperture stop, it is effective to correct the on-axis and off-axis chromatic aberrations.
In the present invention, a diffractive optical surface is formed on any one of the object-side surface of the 1 st lens to the object-side surface of the 3 rd lens.
In the lens structure of the present invention, in order to obtain the chromatic aberration correction effect, a material having negative power and large chromatic dispersion is used for the 2 nd lens. However, only by the combination of materials, the correction effect is limited, and color aberration remains. Therefore, in order to effectively reduce the residual chromatic aberration, the present invention can form the diffractive optical surface at the most appropriate position of the lens system, and can correct the on-axis and off-axis chromatic aberration well.
In the present invention, all the lenses are made of a plastic material for the purpose of easy manufacturing and cost reduction. It is well known that there are limitations on the plastic materials that can be selected in optical systems. That is, the plastic material cannot be required to have high refractive index and low dispersion characteristics as in the case of the glass material. Conventionally, when all lenses are made of a plastic material, it has been difficult to simultaneously and totally correct each aberration, field curvature (field curvature), and chromatic aberration. In the present invention, the diffractive optical surface functions to appropriately correct chromatic aberration, and thus correction of various aberrations other than chromatic aberration is facilitated. Therefore, even if all the lenses are made of a plastic material, a low-cost image pickup lens with good aberration correction can be realized.
In the imaging lens having the above configuration, the 1 st lens is a biconvex lens, the 2 nd lens is a biconcave lens, the 3 rd lens is a meniscus lens having a positive refractive power with a concave surface facing the object side, and the 4 th lens is a biconcave lens, and an aperture stop is disposed on the object side surface of the 1 st lens.
An effect of making the 1 st lens a lenticular lens will be described. Since the 3 rd lens and the 4 th lens are located near the image forming surface, the light beam passing area for forming an image on the optical axis is narrow, and the contribution to the axial aberration correction is small. Therefore, correction of chromatic aberration on the axis becomes performed by the 1 st lens and the 2 nd lens, and it is necessary to set the power of the 1 st lens to be strong. Here, in order to suppress the generation of spherical aberration and tolerance sensitivity of the 1 st lens and correct other aberrations with good balance, it is effective to make the 1 st lens biconvex.
Further, the 2 nd lens is a biconcave lens, which performs chromatic aberration correction while performing correction of astigmatism (astigmatism) and coma aberration. The object-side surface of the 2 nd lens preferably has a larger radius of curvature than the image-side surface. This makes it possible to effectively correct chromatic aberration of magnification and off-axis aberrations. However, when the object-side surface of the 2 nd lens is set to have a larger radius of curvature than the image-side surface, the off-axis aberration tends to be deteriorated, as compared with the case where the aperture ratio is large, the field angle is wide, and the total optical length is shortened. If the negative power of the image-side surface of the 2 nd lens element is too strong, the tolerance sensitivity tends to be strict. These problems are solved in the present invention by forming the diffractive optical surface at an appropriate position.
Further, the 3 rd lens is a meniscus lens having a concave surface on the object side and a positive refractive power, and the 4 th lens is a biconcave lens having a negative refractive power, whereby the total optical length is shortened and various aberrations relating to off-axis optics are corrected well. By making the 3 rd lens a meniscus lens having a positive refractive power with its concave surface facing the object side, it is possible to suppress an increase in the total optical length while maintaining an appropriate back focal length. Further, by making the 4 th lens a biconcave lens, reduction of distortion and telecentricity of the angle of the principal ray incident on the image pickup element are ensured.
Further, by disposing the aperture stop on the object-side surface of the 1 st lens, the angle of the principal ray incident on the imaging element can be suppressed within a certain range.
Further, the imaging lens configured as described above is characterized by satisfying the following conditional expressions:
(1)0.83<f/f12<1.04
(2)-0.05<f/f34<0.08
(3)-0.07<f/(V2·f2)+f/(Vd·fd)<-0.03
(4)-0.01<f/fd<0.15
wherein,
f: the focal length of the whole system;
f12: the combined focal length of the 1 st lens and the 2 nd lens;
f34: the combined focal length of the 3 rd lens and the 4 th lens;
f2: focal length of the 2 nd lens;
fd: the focal length of the diffractive optical surface;
V2: abbe number of e-line of 2 nd lens material;
Vd: abbe number of e-line of the diffractive optical surface.
The conditional expression (1) is a condition for suppressing spherical aberration and correcting axial chromatic aberration by setting the combined power of the 1 st lens and the 2 nd lens to a value close to the power of the entire system. If the lower limit value of the conditional expression (1) is less than "0.83", the correction of each aberration, the large aperture ratio, and the wide field angle are advantageous, but the total optical length is long, and therefore, the miniaturization is difficult. On the other hand, if the upper limit value is exceeded by "1.04", the combined power of the 1 st lens and the 2 nd lens becomes too strong, and it becomes difficult to correct each aberration, increase the aperture ratio, and widen the field angle.
Conditional expression (2) makes it easy to shorten the total optical length, secure an appropriate back focal length, correct distortion, and control the incident angle of the principal ray to the imaging element by setting the combined focal power of the 3 rd lens and the 4 th lens to a value close to 0. If the value is less than the lower limit value "-0.05" of conditional expression (2), the total optical length is favorably shortened, but the aberration becomes large in the positive direction and the incident angle of the principal ray also becomes large, so that it is difficult to correct the aberration. On the other hand, if the upper limit value is exceeded "0.08", the total optical length becomes long, and it becomes difficult to secure the back focal length.
The conditional expression (3) is a condition for specifying the relationship between the refractive power of the 2 nd lens and the paraxial refractive power of the diffractive optical surface and realizing the optimum chromatic aberration correction. If the value is less than the lower limit value "-0.07" of the conditional expression (3), the refractive power of the 2 nd lens and the diffractive optical surface for correcting chromatic aberration becomes excessive, and it becomes difficult to correct chromatic aberration. On the other hand, if the value exceeds the upper limit value of "-0.03", the refractive power is rather insufficient, and therefore it is difficult to correct chromatic aberration at this time.
It is known that chromatic aberration correction in a thin lens of 2-piece construction is given by the following equation.
V1·f1=-V2·f2
Wherein,
V1: abbe number of 1 st lens
f1: focal length of 1 st lens
V2: abbe number of 2 nd lens
f2: focal length of 2 nd lens
For example, if the focal length of the whole system is 1.0V1=56.7、V2If =26.0, f is easily obtained1=0.5414、f2=-1.1808、1/(V2·f2) = -0.033. Similarly, if the 2 nd lens is made to be a diffractive optical surface and V is given2= -3.326, then f is obtained1=1.0588、f2=18.01、1/(V2·f2) = -0.017. The position of the 2 nd lens in the present invention is arranged at a distance most suitable from the aperture stop. At this time, the value of conditional expression (3) is an absolute value larger than the value of the 2 thin lenses, but the value can be changed by combining with the diffractive optical surface. In the present invention, the diffractive optical surface located farthest from the aperture stop is the surface on the object side of the 3 rd lens. The area through which the light passes is condensed by the lens, and therefore, the light becomes about 50% of the area of the light passing through the aperture stop. In this case, the value "-0.07" of conditional expression (3) is set to the lower limit so that chromatic aberration correction can be performed to the same extent as the thin lens.
The conditional expression (4) is a condition for defining a range of the refractive power of the diffractive optical surface at the paraxial region and for achieving favorable chromatic aberration correction in combination with the conditional expression (3). If the value is less than the lower limit value "-0.01" of the conditional expression (4), the burden of chromatic aberration correction on the axis of the 2 nd lens becomes large, and it becomes difficult to correct aberration. On the other hand, if the upper limit value is exceeded by "0.15", the axial chromatic aberration correction becomes excessive, that is, the short wavelength increases in the + direction with respect to the reference wavelength, the balance between the axial chromatic aberration and the magnification chromatic aberration is lost, and it becomes difficult to perform a satisfactory chromatic aberration correction.
Since the optical path difference function is defined by a high-order equation, the power at the paraxial region of the diffractive optical surface does not necessarily directly represent the state of actual chromatic aberration correction. However, the position where the diffractive optical element is provided and the optical power at the paraxial region tend to be constant. That is, when the diffractive optical surface is disposed on the side close to the object side, the power near the axis becomes large mainly for correcting chromatic aberration on the axis. In contrast, when a diffractive optical surface is disposed on a surface far from the object side, it is mainly necessary to correct chromatic aberration of magnification, and therefore, it is not necessary to increase the power at the paraxial region. In the case of the 3 rd lens and the 4 th lens according to the present invention, since the off-axis aberration correction amount is large and the change in the chromatic aberration of magnification due to the aspherical surface is large, the power at the paraxial region in the diffractive optical surface takes a small value and the higher-order term of the optical path difference function takes a large value.
According to the present invention, by arranging the diffractive optical surface at the most appropriate position in the imaging lens having the 4-piece structure, it is possible to provide a small-sized and high-performance imaging lens in which chromatic aberration is corrected more favorably than in the past and which is compatible with other aberration corrections.
In addition, the use of a plastic material for all the lenses can reduce the cost.
Drawings
Fig. 1 is a sectional view of an imaging lens according to embodiment 1 of the present invention.
Fig. 2 is each aberration diagram of the imaging lens according to embodiment 1 of the present invention.
Fig. 3 is a sectional view of an imaging lens according to embodiment 2 of the present invention.
Fig. 4 is each aberration diagram of the imaging lens according to embodiment 2 of the present invention.
Fig. 5 is a sectional view of an imaging lens according to embodiment 3 of the present invention.
Fig. 6 is each aberration diagram of the imaging lens according to embodiment 3 of the present invention.
Fig. 7 is a sectional view of an imaging lens according to embodiment 4 of the present invention.
Fig. 8 is an aberration diagram of the imaging lens according to embodiment 4 of the present invention.
Fig. 9 is a sectional view of an imaging lens according to embodiment 5 of the present invention.
Fig. 10 is each aberration diagram of the imaging lens according to embodiment 5 of the present invention.
Fig. 11 is a sectional view of an imaging lens according to embodiment 6 of the present invention.
Fig. 12 is each aberration diagram of the imaging lens according to embodiment 6 of the present invention.
Description of the reference numerals
ST aperture diaphragm
Object-side surface of R1 first lens 1
Surface on the image side of the R2 th lens 1
Object-side surface of R3 (2 nd lens)
Surface on the image side of the 2 nd lens of R4
Object-side surface of R5 No. 3 lens
Surface on the image side of the R6 No. 3 lens
Object-side surface of R7 th lens 4
Surface on the image side of the 4 th lens of R8
R9 and R10 glass surface protection
d 1-d 9 shaft upper surface interval
X-ray axis
S image plane
The DOE forming the surface of the diffractive optical surface
Detailed Description
Hereinafter, embodiments embodying the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1, 3, 5, 7, 9, and 11 are sectional views of lenses corresponding to examples 1 to 6 of the embodiment of the present invention. Since the basic lens configurations of the respective embodiments are the same, the lens configuration of the imaging lens of the present embodiment will be described with reference to the sectional view of the lens of embodiment 1.
As shown in fig. 1, the imaging lens of the present invention includes a 1 st lens L1, a 2 nd lens L2, a 3 rd lens L3, and a 4 th lens L4, wherein the 1 st lens L1 is a biconvex lens, the 2 nd lens L2 is a biconcave lens, the 3 rd lens L3 is a meniscus lens having a concave surface facing the object side and having a positive refractive power, and the 4 th lens L4 is a biconcave lens. Further, both surfaces of all the lenses are formed by aspherical surfaces, and all the lenses are formed by plastic materials.
In all of the embodiments, the periphery of the effective diameter of the object-side surface R1 of the 1 ST lens L1 also serves as an aperture stop (diaphragm) ST. Further, a protective glass made of R9 and R10 is disposed between the image plane S and the image plane R8 on the image side of the 4 th lens L4. In the sectional view, d1, d2, …, and d9 denote plane intervals, X denotes an optical axis, and DOE denotes a diffractive optical surface.
In the present embodiment, all the lens surfaces are formed to be aspherical, and the aspherical shape adopted for these lens surfaces is Z as an axis in the optical axis direction, Y as a height in a direction orthogonal to the optical axis, К as a conic coefficient, and A as an aspherical coefficient2iRepresented by the formula 1.
Further, a diffractive optical surface DOE, which is a function of an optical path difference (optical path difference) expressed by equation 2, is formed on any one of the object-side surface R1 of the 1 st lens L1 to the object-side surface R5 of the 3 rd lens L3.
[ mathematical formula 1]
Z = Y 2 R 1 - ( 1 + K ) × Y 2 R 2 + Σ i = 2 10 A 2 i × Y 2 i
[ mathematical formula 2]
Wherein,
p: optical path difference (unit: wavelength)
B2i: coefficients of the optical path difference function (i =1~ n).
Next, an example of the imaging lens according to the present embodiment will be described. In each embodiment, F denotes a focal length of the entire lens system, Fno denotes an F value (F number), and ω denotes a half field angle. In addition, the surface number indicates the number from the object side, R indicates the radius of curvature, d indicates the distance between lens surfaces (surface interval) along the optical axis, n indicates the refractive index for the e-line, and ν indicates the abbe number for the e-line.
[ example 1]
Table 1 below shows basic lens data. In addition, a diffractive optical surface DOE is formed on the object-side surface R5 of the 3 rd lens L3.
[ Table 1]
Surface data
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) | 1.5750 | 0.7000 | 1.53690 | 56.1 |
| 2 | -6.2059 | 0.0394 | ||
| 3 | -9.3660 | 0.4419 | 1.61988 | 25.4 |
| 4 | 3.6306 | 0.6077 | ||
| 5(DOE) | -2.3470 | 0.9602 | 1.54647 | 55.8 |
| 6 | -0.7420 | 0.0682 | ||
| 7 | -31.0000 | 0.4349 | 1.53690 | 56.1 |
| 8 | 0.8712 | 0.5000 | ||
| 9 | ∞ | 0.3000 | 1.51872 | 64.0 |
| 10 | ∞ | 0.7076 | ||
| Image plane | ∞ |
f＝3.905、Fno＝2.4、ω＝36.4°
Next, table 2 below shows the values of the aspherical surface coefficient and each coefficient of the optical path difference function in the diffractive optical surface in example 1.
[ Table 2]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.916
(2)f/f34=0.055
(3)f/(V2·f2)+f/(Vd·fd)=-0.036
(4)f/fd=-0.002
Accordingly, the imaging lens according to embodiment 1 satisfies conditional expressions (1) to (4).
Fig. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of example 1. In these aberration diagrams, the aberration amounts for the respective wavelengths of the F-line (486.13 nm), the e-line (546.07 nm), and the C-line (656.27 nm) are shown in the spherical aberration diagrams, and the aberration amount in the sagittal image plane S and the aberration amount in the meridional image plane T are shown in the astigmatic diagrams, respectively (the same applies to fig. 4, 6, 8, 10, and 12).
As shown in fig. 2, the imaging lens according to embodiment 1 corrects chromatic aberration well, and also corrects other aberrations appropriately.
[ example 2]
Table 3 below shows basic lens data. In example 2, as in example 1, a diffractive optical surface DOE is formed on the object-side surface R5 of the 3 rd lens L3.
[ Table 3]
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) | 1.4948 | 0.6921 | 1.53690 | 56.1 |
| 2 | -6.1721 | 0.0348 | ||
| 3 | -6.1900 | 0.3419 | 1.61988 | 25.4 |
| 4 | 4.2069 | 0.6659 | ||
| 5(DOE) | -2.0009 | 0.9874 | 1.54647 | 55.8 |
| 6 | -0.7591 | 0.1184 | ||
| 7 | -39.0506 | 0.4000 | 1.53690 | 56.1 |
| 8 | 0.9166 | 0.5000 | ||
| 9 | ∞ | 0.3000 | 1.51872 | 64.0 |
| 10 | ∞ | 0.7196 | ||
| Image plane | ∞ |
f＝3.945、Fno＝2.4、ω＝36.1°
Next, table 4 below shows the values of the aspherical surface coefficients and the coefficients of the optical path difference function in the diffractive optical surface in example 2.
[ Table 4]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.943
(2)f/f34=0.024
(3)f/(V2·f2)+f/(Vd·fd)=-0.053
(4)f/fd=0.045
Accordingly, the imaging lens according to embodiment 2 satisfies conditional expressions (1) to (4).
Fig. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens according to example 2. As shown in fig. 4, the imaging lens according to embodiment 2 corrects chromatic aberration well, and also corrects other aberrations appropriately.
[ example 3]
Table 5 below shows basic lens data. In embodiment 3, the diffractive optical surface DOE is formed on the object-side surface R3 of the 2 nd lens L2.
[ Table 5]
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) | 1.9890 | 0.6848 | 1.53690 | 56.1 |
| 2 | 6.5000 | 0.1075 | ||
| 3(DOE) | -54.9999 | 0.5506 | 1.61988 | 25.4 |
| 4 | 3.9159 | 0.5259 | ||
| 5 | 2.0910 | 0.7597 | 1.53690 | 56.1 |
| 6 | -0.8465 | 0.1384 | ||
| 7 | -100.0000 | 0.4988 | 1.53690 | 56.1 |
| 8 | 1.0707 | 0.6945 | ||
| 9 | ∞ | 0.3000 | 1.51872 | 64.0 |
| 10 | ∞ | 0.5000 | ||
| Image plane | ∞ |
f＝3.918、Fno＝2.4、ω＝36.3°
Next, table 6 below shows the values of the aspherical surface coefficients and the coefficients of the optical path difference function in the diffractive optical surface in example 3.
[ Table 6]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.927
(2)f/f34=-0.029
(3)f/(V2·f2)+f/(Vd·fd)=-0.049
(4)f/fd=0.086
Accordingly, the imaging lens according to embodiment 3 satisfies conditional expressions (1) to (4).
Fig. 6 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens according to example 3. As shown in fig. 6, the imaging lens according to embodiment 3 corrects chromatic aberration well, and also corrects other aberrations appropriately.
[ example 4]
Table 7 below shows basic lens data. In embodiment 4, the diffractive optical surface DOE is formed on the object-side surface R1 of the 1 st lens L1.
[ Table 7]
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) (DOE) | 1.4925 | 0.775 | 1.53690 | 56.1 |
| 2 | 5.6022 | 0.040 | ||
| 3 | -5.6025 | 0.285 | 1.61988 | 25.4 |
| 4 | 4.1961 | 0.691 | ||
| 5 | -2.0025 | 0.953 | 1.54647 | 55.8 |
| 6 | -0.7678 | 0.128 | ||
| 7 | -31.7913 | 0.400 | 1.53690 | 56.1 |
| 8 | 0.9400 | 0.500 | ||
| 9 | ∞ | 0.300 | 1.51872 | 64.0 |
| 10 | ∞ | 0.689 | ||
| Image plane | ∞ |
f＝4.0038、Fno＝2.43、ω＝35.6°
Next, table 8 below shows the values of the aspherical surface coefficients and the coefficients of the optical path difference function in the diffractive optical surface in example 4.
[ Table 8]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.964
(2)f/f34=-0.023
(3)f/(V2·f2)+f/(Vd·fd)=-0.042
(4)f/fd=0.002
Accordingly, the imaging lens according to embodiment 4 satisfies conditional expressions (1) to (4).
Fig. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens according to example 4. As shown in fig. 8, the imaging lens according to embodiment 4 corrects chromatic aberration well, and also corrects other aberrations appropriately.
[ example 5]
Table 9 below shows basic lens data. In embodiment 5, the diffractive optical surface DOE is formed on the image-side surface R2 of the 1 st lens L1.
[ Table 9]
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) | 1.5044 | 0.798 | 1.53690 | 56.1 |
| 2(DOE) | -7.9825 | 0.031 | ||
| 3 | 7.9875 | 0.280 | 1.61988 | 25.4 |
| 4 | 4.1953 | 0.686 | ||
| 5 | -2.0035 | 0.977 | 1.54647 | 55.8 |
| 6 | -0.7733 | 0.136 | ||
| 7 | -31.0000 | 0.400 | 1.53690 | 56.1 |
| 8 | 0.9400 | 0.500 | ||
| 9 | ∞ | 0.3000 | 1.51872 | 64.0 |
| 10 | ∞ | 0.6519 | ||
| Image plane | ∞ |
f＝3.9688、Fno＝2.42、ω＝35.7°
Next, table 10 below shows the values of the aspherical surface coefficients and the coefficients of the optical path difference function in the diffractive optical surface in example 5.
[ Table 10]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.971
(2)f/f34=-0.039
(3)f/(V2·f2)+f/(Vd·fd)=-0.042
(4)f/fd=0.022
Accordingly, the imaging lens according to embodiment 5 satisfies conditional expressions (1) to (4).
Fig. 10 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens according to example 5. As shown in fig. 10, the imaging lens according to embodiment 5 corrects chromatic aberration well, and also corrects other aberrations appropriately.
[ example 6]
Table 11 below shows basic lens data. In embodiment 6, the diffractive optical surface DOE is formed on the image-side surface R4 of the 2 nd lens L2.
[ Table 11]
| Number of noodles | R | d | n | v |
| Object surface | ∞ | ∞ | ||
| 1 (Aperture) | 1.5205 | 0.744 | 1.53690 | 56.1 |
| 2 | -7.3061 | 0.045 | ||
| 3 | 7.5446 | 0.286 | 1.61988 | 25.4 |
| 4(DO E) | 4.1953 | 0.656 | ||
| 5 | -1.9661 | 1.007 | 1.54647 | 55.8 |
| 6 | 0.7573 | 0.114 | ||
| 7 | -31.0000 | 0.428 | 1.53690 | 56.1 |
| 8 | 0.9400 | 0.500 | ||
| 9 | ∞ | 0.300 | 1.51872 | 64.0 |
| 10 | ∞ | 0.682 | ||
| Image plane | ∞ |
f＝3.9688、Fno＝2.42、ω＝35.7°
Next, table 12 below shows the values of the aspherical surface coefficient and each coefficient of the optical path difference function in the diffractive optical surface in example 6.
[ Table 12]
Aspheric data
The values of the conditional expressions are shown below.
(1)f/f12=0.953
(2)f/f34=-0.024
(3)f/(V2·f2)+f/(Vd·fd)=-0.047
(4)f/fd=0.045
Accordingly, the imaging lens according to embodiment 6 satisfies conditional expressions (1) to (4).
Fig. 12 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens according to example 6. As shown in fig. 12, the imaging lens according to embodiment 6 corrects chromatic aberration well, and also corrects other aberrations appropriately.
Therefore, the imaging lens according to the above embodiment can achieve both chromatic aberration correction and other various aberration corrections with a small number of constituent elements, and can achieve a large aperture ratio and high performance.
The present invention is applicable to a small-sized image pickup device having a higher number of pixels, and is particularly effective in the field of a small-sized image pickup lens mounted on a mobile information terminal such as a mobile phone.
Claims (2)
1. An imaging lens for an imaging element,
a 1 st lens, a 2 nd lens, a 3 rd lens, and a 4 th lens are arranged in this order from the object side, the 1 st lens is a biconvex lens, the 2 nd lens is a biconcave lens, the 3 rd lens is a meniscus lens having a positive refractive power with a concave surface facing the object side, the 4 th lens is a biconcave lens in which both surfaces of all lenses are formed by aspherical surfaces, and a diffractive optical surface that performs a chromatic aberration correction function is formed on any one of the object side surface of the 1 st lens and the object side surface of the 3 rd lens, and all lenses are made of a plastic material, and the following conditional expressions (1) to (4) are satisfied:
(1)0.83<f/f12<1.04
(2)-0.05<f/f34<0.08
(3)-0.07<f/(V2·f2)+f/(Vd·fd)<-0.03
(4)-0.01<f/fd<0.15
wherein,
f: the focal length of the whole system;
f12: the combined focal length of the 1 st lens and the 2 nd lens;
f34: the combined focal length of the 3 rd lens and the 4 th lens;
f2: focal length of the 2 nd lens;
V2: abbe number of e-line of the 2 nd lens;
Vd: abbe number of e-line of the diffractive optical surface;
fd: focal length of the diffractive optical surface.
2. The imaging lens according to claim 1,
an aperture stop is disposed on the object-side surface of the 1 st lens.
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| TWI485463B (en) * | 2013-11-01 | 2015-05-21 | Largan Precision Co Ltd | Image lens assembly, image capturing device and mobile terminal |
| JP2015102849A (en) * | 2013-11-28 | 2015-06-04 | カンタツ株式会社 | Image capturing lens |
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| CN104570296B (en) * | 2014-12-17 | 2018-11-27 | 深圳市亿思达科技集团有限公司 | ultra-short focus projection lens |
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| CN111308652B (en) * | 2020-02-24 | 2021-07-30 | 诚瑞光学(常州)股份有限公司 | Image pickup optical lens |
| CN111552138A (en) * | 2020-05-29 | 2020-08-18 | Oppo广东移动通信有限公司 | Under-screen camera, imaging method and terminal |
| CN112034596B (en) * | 2020-09-24 | 2025-03-18 | 江西晶超光学有限公司 | Optical lens, imaging module and electronic device |
| CN113281880B (en) * | 2021-05-10 | 2022-08-23 | 江西晶超光学有限公司 | Imaging system, lens module and electronic equipment |
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| US9268115B2 (en) | 2016-02-23 |
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| CN102854610A (en) | 2013-01-02 |
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